Multi-motor drive drafting synchronization control
In the four-way transmission (three-way drafting and crimping) of the chemical fiber spinning equipment, the determination of the draft ratio must be based on the speed synchronization of the four transmission motors. Under normal circumstances, there is a main given signal. The goal of synchronous control is to evenly distribute this signal to the four inverters M1, M2, M3 and M4 according to the requirements of the draft ratio, to ensure that the four transmissions are accelerated and constant. The proportionality of synchronization can be maintained during speed or deceleration.
The following mainly discusses three synchronous control schemes that are currently more commonly used.
3.1 Analog Synchronous Control
When each drive unit in a complete machine or a production line is driven by an independent inverter, in order to ensure that the units are synchronized and coordinated under a master speed setting (here is a fixed draft ratio), Configure the sync controller. The synchronous controller can separately set the transmission speed of each unit to realize the synchronous operation of each unit at a certain proportional speed. The total master setting voltage (determined by the potentiometer) can achieve soft start by a given integrator output. Soft parking.
The synchronous controller can output multiple analog signals to the inverter (here, VF1-VF4). The analog input setting method is a method with high control precision. Generally, the resolution of the voltage "11bit+symbol" or current "10bit" can be achieved.
3.2 pulse signal synchronization control
In electronic technology, a pulse signal is a pulse signal that is continuously emitted at a certain voltage interval and at a certain time interval. We refer to the time interval between the first pulse and the second pulse as the period; and the number of pulses generated in a unit time (such as 1 second) is called the frequency.
Normally, the maximum input pulse frequency can be selected from 0.1KHz to 50KHz. The VF1 inverter outputs the number of synchronous pulses to VF2 under the control of the master potentiometer. VF2 accepts the number of pulses and simultaneously outputs the number of synchronous pulses to VF3 until VF4. Due to the digital processing technology of pulse signals and strong anti-interference ability, it is also widely used in synchronous control.
3.3 Communication bus synchronization control
Setting the frequency through the network is a high-precision frequency setting, which has the advantages of high communication speed, stable and reliable, simple wiring, etc., and in analog control, the output end passes through a digital-to-analog converter and enters the input through the wire. The terminal (inverter) needs to go through an analog-to-digital converter to participate in the control. The difference between the two converter bits and the wire loss may cause a certain error, and the communication transmission is directly digital, no conversion, no error, no loss during transmission, and the response speed rate is also high.
Under normal circumstances, the synchronous control can adopt the asynchronous communication control mode of RS485 bus, as shown in Figure (3). The built-in RS485 of the inverter can easily realize the communication with the host computer. At the same time, it can also hang the field bus or LAN, and exchange information through the network. There are mainly different networks and bus forms such as PROFIBUS, Modbus and FF, but it must be equipped. Use a dedicated interface card.
4 Conclusion
The application of frequency conversion technology in chemical fiber post-spinning equipment should be combined with the requirements of the process itself. The multi-motor transmission control structure with shared DC bus method can solve the problem of continuous power generation of one and two channels, and adopt synchronous control to achieve constant traction. Stretch ratio. This program has been successfully applied in the technical transformation of a number of short fiber post-spinning equipment.
Please pay attention to Long Life Dc Motor
